The above advice is very useful
Make 3 tables, and update them constantly. Subjects you like, subjects you are good at, and professions that took your interest (maybe from family, tv etc). See if any align. You can eliminate hundreds of professions just by realising you dislike a school subject
Something I will say is to not put too much pressure finding the perfect career. Chances are if you liked and enjoyed one career you would also like and enjoy another because of the transferable skills. Try to focus on a ball park for now
In the US you aren't allowed to study a professional degree (medicine, law etc) until you do a generic undergraduate beforehand anyway
A few close friends of mind did very different undergraduate degrees compared to the careers they are in now. They didn't regret it as they enjoyed their initial degrees even though they realised career wise it wasn't for them
If you do, in the worst case scenario,realise the degree you are on isn't for you just focus on making the most of it and getting the best grades to help any conversions to go smoothly.
Your life doesn't start when are fully qualified, it will just be a part of your life. Enjoy your time figuring out your dream/getting to your dream,but just do not become complacent as you'll see that the you'll be behind everyone else if you suddenly work out what you want to do but didn't do anything until then
Work experience and university open days in areas that interest you help a lot too